In the treatment of visual acuity deficiencies, correction by means of eyeglasses or contact lenses is used by a large percentage of the population. Such visual acuity deficiencies include hyperopia or far-sightedness, myopia or near-sightedness, astigmatisms (caused by asymmetry of a patient's eye) and presbyopia (caused by loss of accommodation by the crystalline lens). To alleviate the burden of wearing eyeglasses and/or contact lenses, surgical techniques have been developed for altering the shape of a patient's cornea in an attempt to correct refractive errors of the eye. Such surgical techniques include photorefractive keratectomy (PRK), LASIK (laser-assisted in-situ keratomileusis), as well as procedures such as automated lamellar keratoplasty (ALK) or implanted corneal rings, implanted contact lenses, and radial keratotomy (RK). These procedures are intended to surgically modify the curvature of the cornea to reduce or eliminate visual defects. The popularity of such techniques has increased greatly, but such techniques still carry risk in both the procedures themselves, as well as post-surgical complications.
Alternatives to permanent surgical procedures to alter the shape of the cornea include corneal refractive therapy (CRT) and orthokeratology (also known as “ortho-K”), in which a modified contact lens is applied to the eye to alter the shape or curvature of the cornea by compression of the corneal surface imparted by the corrective lens.